On lower bounds for the Kirchhoff index

Abstract

Let G be a simple graph of order n ≥ 2 with m edges. Denote by d1 ≥ d2 ≥ · · · ≥ dn > 0 the sequence of vertex degrees and by μ1 ≥ μ2 ≥ · · · ≥ μn−1 > μn = 0 the Laplacian eigenvalues of the graph G. Lower bounds for the Kirchhoff index, Kf(G) = n Σ −1 i=1 1 μi, are obtained.